"Easy open" features have been provided in the sealed regions of formed, filled, and sealed pouches in the past to facilitate opening of the sealed pouches. French Pat. No. 1,394,228 issued to Mauvernay on Feb. 22, 1965 is representative of such prior art practice. A line of perforations or a slit is formed in a sealed lateral seam spaced slightly below a sealed top seam that intersects perpendicularly the seam with the perforations or slit in it. A tear is initiated to open the pouch by twisting the lateral seam either across the perforations or parallel along the slit. The applied stress is thereby concentrated on the weakest area of the lateral seam, causing a tear to propagate from the perforations or slit, across the lateral seam and into the pouch in a direction generally parallel to the top seam. No method or apparatus for providing the perforations or slit is disclosed.
These prior art "easy open" features have been formed before the pouch is separated from a continuous web of filled and sealed pouches, interconnected at their lateral edges. For example, U.S. Pat. No. Re. 27,913 issued to Hutcheson on Feb. 5, 1974 discloses a process for forming a circular hole in a pouch seam using an electric eye which, when it recognizes indicia printed on the pouch, operates a reciprocating hole punching means. However, the web undergoes movement relative to the hole punching means before the transverse cut is effected downstream of the hole punching means. Accordingly, the accuracy of hole placement relative to the severed edge of the pouch with such a device is entirely dependent upon the consistency of response time of both the electric eye and the web advancing means.
U.S. Pat. No. 3,196,728 issued to Snow on July 27, 1965 discloses a machine for simultaneously punching a package support hole and an adjacent slit in a plastic package to weaken the package and thereby permit easy removal of the package when it is supported on a hook. The device disclosed in Snow operates in a manner similar to a conventional office hole punch.
It is also known in the prior art to provide cutting means for transversely cutting pouches comprised of thermoplastic film from a continuous web of interconnected pouches. Said transverse cutting is performed by means of a rotating spider employing heated metallic wires at spaced locations about its periphery while said web is secured to the periphery of a cylindrical drum on which said pouches are filled and sealed. U.S. Pat. No. 3,054,441 issued to Gex et al. on Sept. 18, 1962 describes such mechanism in detail. It is also known in the prior art to equip the transverse pouch cutting spider generally shown in FIG. 1 of the Gex et al. patent with phonograph needles mounted on radially extending arms located intermediate the heated wire cutting elements. The phonograph needles serve to puncture the body portions of the uppermost layer of thermoplastic film to allow air trapped within the pouch during the forming operation to escape. Puncturing of the body portion of the pouch by the needle is completed after the leading edge of the pouch has been severed, but prior to severance of the trailing edge of the pouch from the web. Accordingly, the portion of the pouch being punctured is not in tension during the puncturing operation.
A film perforating means utilized in conjunction with the pouch forming and transverse cutting mechanism generally disclosed in the aforementioned patent to Gex et al. is also disclosed in U.S. Pat. No. 3,208,192 issued to Schaeffer on Sept. 28, 1965. In the Schaeffer apparatus, the perforations are provided by means of a rotating spider having pointed arms, said spider being located ahead of the transverse cutting means. The spider is driven in timed relation to the drum so as to perforate only the body portions of a first web used to form said pouches. The body perforations formed in the web which contacts the exposed periphery of the drum permit air to be evacuated from within the pouches after filling and sealing, but prior to transverse cutting.
The prior art fails, however, to disclose simple and reliable web cutting means having punching means operatively connected therewith for continuously forming precisely registered "easy open" apertures in the sealed region of a pouch while the pouch is being severed from a continuously moving web. Furthermore, the prior art fails to disclose such means wherein said web is held stationary relative to said transverse cutting and said aperture punching means until both operations have been completed.
As will be appreciated by those skilled in the art, it is highly desirable that the stress concentrating aperture be accurately positioned with respect to the edge of the pouch. If the aperture is positioned too close to the pouch edge, it will be too easy to open the pouch, thereby increasing the likelihood that the pouch will be accidentally opened when handled or in transit. On the other hand, if the aperture is positioned too far from the pouch edge it may be difficult for the user to initiate a tear to open the bag, or even worse, the product-containing portion of the pouch may be penetrated. This is particularly undesirable where the product contained within the pouch is subject to degradation upon exposure to the atmosphere.
It is also desirable that the aperture have at least one internal area of stress concentration to facilitate initiating a tear when relatively low stress levels are applied thereto.
Accordingly, it is an object of the present invention to provide a flexible pouch having a stress concentration aperture precisely located in one of its seal areas, said aperture exhibiting a strong tendency to initiate a tear in the direction of the severed edge of the pouch rather than toward the pouch body when relatively low stress levels are applied thereto. It is another object of the present invention to provide simple and reliable method and apparatus for continuously forming precisely located stress concentration apertures in the sealed areas of pouches as they are severed from a continuous web of interconnected pouches. It is also an object of the present invention to ensure that the aperture is precisely positioned with respect to the edge of each pouch in automatic fashion, regardless of variations in web speed. It is still another object to provide a continuous process for forming precisely located stress concentration apertures wherein the means for providing said apertures are operatively connected with the means employed to sever said pouches from said web, said web being held stationary relative to said cutting and said aperturing means until both operations have been completed. It is yet another object of the present invention to provide such method and apparatus which will function reliably, even where tough and/or stretchy pouch materials are employed.